1. Field of the Invention
The present invention relates to multimedia communications. More particularly, the present invention relates to the efficient delivery of multimedia data to multicast group(s) over a diverse computer network.
2. Description of the Related Art
With the proliferation of connections to the internet by a rapidly growing number of users, the viability of the internet as a widely accepted medium of communication has increased correspondingly. Bandwidth requirements can vary significantly depending on the content of multimedia data being delivered and computational capacity of the client computers receiving the multimedia data. Hence, the ability to efficiently deliver multimedia data to a number of client computers over the internet is limited by how the available bandwidth capacity of the network is utilized to provide video information to a diverse group of client computer.
In a typical video delivery scheme, for each video stream, a point-to-point connection is provided by the network between the server and each client computer. From the network""s perspective, this scheme is inefficient especially when similar content is delivered to a number of client computers. A more efficient method is to multicast xe2x80x9cblindlyxe2x80x9d over the network without any feedback from the client computers, in a manner similar to a wireless television broadcast. One such conventional video encoding and decoding system is described in xe2x80x9cAn End-to-End Software only Scalable Video Delivery System,xe2x80x9d published in Proc. Networks and Operating System Support for Digital Audio and Video, April 1995. Instead of establishing individual point-to-point connections for each client computer, the server multicasts an entire embedded stream for different resolutions and frame rates onto the network as a set of trees. However, xe2x80x9cthe server has no idea about the decoders at the destinationsxe2x80x9d (page 136, lines 4-5) (emphasis added). Primary traffic management is performed by not adding branches of the trees carrying the less important bit streams to the lower bandwidth portions of the network. In addition, switches and routers of the network may react to temporary network congestion by dropping packets carrying the less important bits from the embedded stream.
Unfortunately, with the push multicast model described above, since xe2x80x9cthe destinations [decoders] are slaved to the flow from the server with no feedbackxe2x80x9d (page 137, lines 46-47) (emphasis added), the server is incapable of adapting to the actual needs of individual and/or sub-groups of client computers. Packets carrying less important bits are sent to client computers so long as the corresponding portion of the network is capable of carrying the additional information. In other words, the server ignores the actual needs of the client computers. For example, a user at any particular client computer may not be interested in receiving a high resolution and/or a high frame rate video stream, even if the network is capable of supporting the higher bit stream. Alternatively, a particular client computer or its modem may be incapable of processing the higher resolution and/or faster frame rate video stream. As a result, a considerable amount of unused or underutilized information is wastefully multicasted over the network and unnecessarily consumes valuable network resources.
In view of the foregoing, there are desired improved techniques for adaptively providing scalable multimedia data to a broad range of client computers while efficiently utilizing the valuable network resources.
A method of interactively providing a number of client computers with a dynamically selectable and scalable range of multimedia data over a diverse computer network including local area networks (LANs) wide area networks (WANs) such as the internet.
Multimedia data is provided by a server to the client computers includes a base layer and one or more enhancement layers. Enhancement layers can be spatial and/or temporal in nature. Depending on the implementation, the server may also provide information about the multimedia data to the client computers.
In accordance with one aspect of the invention, the server splits the multimedia data for streaming via multiple multicast group (MMG) addresses. Information about the portion of the multimedia data carried by each MMG is broadcasted to the client computers. Armed with the information about the multimedia data, client computers can intelligently join and leave MMGs as needed.
In some embodiments, the client computers provide feedback about the usage and/or need for the multimedia data, enabling the server to right-size, e.g., grow and/or prune, the multimedia data for network efficiency. With right sizing, the content of the base layer may be increased or decreased with the corresponding growing and pruning of the enhancement layers. Enhancement layers may also be grown and/or pruned independently of the base layer, i.e., without a corresponding change in the base layer.